Mitral Annuloplasty Ring Having Upward Bows

ABSTRACT

Methods of implanting an annuloplasty ring to correct maladies of the mitral annulus that not only reshapes the annulus but also reconfigures the adjacent left ventricular muscle wall. The ring may be continuous and is made of a relatively rigid material, such as Stellite. The ring has a generally oval shape that is three-dimensional at least on the posterior side. A posterior portion of the ring rises or bows upward from adjacent sides to pull the posterior aspect of the native annulus farther up than its original, healthy shape. In doing so, the ring also pulls the ventricular wall upward which helps mitigate some of the effects of congestive heart failure. Further, one or both of the posterior and anterior portions of the ring may also bow inward. The methods include securing the annuloplasty ring with the anterior portion against the annulus anterior aspect and the posterior portion against the annulus posterior aspect so that the ring posterior portion elevates, and may also pull radially inward, the annulus posterior aspect and corrects the mitral regurgitation.

RELATED PATENTS

The present application is a continuation of U.S. application Ser. No.10/968,323, filed Oct. 18, 2004, which is a continuation of U.S. Pat.No. 6,805,710, filed Oct. 9, 2002, which claims priority under 35 U.S.C.§119(e) from Provisional Patent Application No. 60/332,353, filed Nov.13, 2001, the disclosures of which are incorporated by reference hereinin their entireties.

FIELD OF THE INVENTION

The present invention relates generally to medical devices, specificallyto an annuloplasty ring and related procedure for surgicallyreconstructing and molding the mitral valve annulus of a patient'sheart. More specifically, this invention relates to a mitral valverepair device and corresponding technique that involve over-correctingdefects in the mitral valve annulus so as to remodel theleft-ventricular geometric relationship.

BACKGROUND OF THE INVENTION

Congestive heart failure (CHF) is a leading cause of hospitalization anddeath in the United States, and its incidence is increasing. Secondarymitral regurgitation (MR), a complication of end-stage cardiomyopathy,refers to the backflow of blood from the left ventricle to the leftatrium resulting from imperfections in the mitral valve. When the mitralvalve allows blood to flow backward into the left atrium, the leftventricle must pump progressively harder to circulate blood throughoutthe body, which in turn promotes CHF. While heart transplantation isconsidered a standard treatment for select patients with severe CHF andend-stage heart disease, it is only applicable to a small percentage ofpatients because of the small number of available donor hearts andsurgical risks for weaker patients. Accordingly, alternative medical andsurgical strategies are evolving to treat such conditions.

As seen in FIGS. 1A and 1B, the mitral aimulus 20 represents thejunction of the fibrous and muscular tissue that joins the left atrium.LA and left ventricle LV. The average human mitral annularcross-sectional area is 5-11 cm². The mitral valve is a bicuspid valvehaving a large posterior leaflet 22 that coapts or meets with a smalleranterior leaflet 24. The anterior aspect 26 of the annulus, which is incontinuity with the fibrous skeleton of the heart, has limitedflexibility, whereas the posterior aspect 28 of the annulus, which isnot attached to any rigid surrounding structures, has more flexibility.For the purpose of discussion, the mitral annulus 20 lies generally in adatum plane 30 (FIG. 1A) at an angle with respect to a datum plane 32 inwhich the aortic valve 34 is generally oriented. These datum planes 30,32 can be defined as being perpendicular to the average blood flowthrough the respective valves. During systole the mitral annulus 20assumes a generally elliptical shape as shown in FIG. 1B, and is able tocontract and decrease in diameter, whereas, in diastole, it assumes amore circular shape and opens to permit blood to fill the left ventricleLV. Annular flexibility allows for increased leaflet coaptation duringsystole and increased annular orifice area during diastole.

In MR, dilation typically occurs along the more flexible posterioraspect 28 of the annulus, as seen in FIGS. 2A and 2B. Some patientsexperiencing a drop h of the posterior aspect 28 of the mitral valveannulus, as seen in FIG. 2A, and consequent relaxation of the posteriormuscle wall 36 of the left ventricle LV. FIG. 2B illustrates thelengthening of the anterior-posterior dimension 38 and subsequent lossof coaptation between the posterior and anterior leaflets 22, 24.

MR leads to a cycle of continuing volume overload of the already dilatedleft ventricle LV, progression of annular dilation, increased leftventricle wall tension, increasing degrees of MR and worsening CHF. InMR, the regurgitant volume ejected into the left atrium LA is dependentupon mitral orifice size, ventricular/atrial pressure gradient and heartrate. The regurgitant flow into the left atrium LA increases left atrialpressure, which leads to atrial enlargement and an increase incompliance, and decreases forward systemic flow. Left atrial pressuresrise during systole and decline in diastole.

FIGS. 3A and 3B illustrate the use of a Carpentier-Edwards PHYSIOannuloplasty ring 40 to restore the original healthy shape of the mitralannulus 20. The ring 40 is typically semi-rigid and planar and restoresthe primary anterior-posterior dimension 38′ of the mitral annulus 20.

Various other interventions have been used to alter the size of theregurgitant orifice area. An increase in preload or afterload, or adecrease in contractility, results in dilation of the LV and an increasein regurgitant orifice area. The complex relationship between mitralannular area and leaflet coaptation may explain why some studies havefound that performing a “valvular” repair, with an undersized flexibleannuloplasty ring, has helped with a “muscular” problem of the leftventricle. For example, in a study conducted between 1993-1999 at theUniversity of Michigan, 92 patients with end-stage cardiomyopathy andrefractory MR underwent mitral valve repair with an “undersized”annuloplasty rings having a circumference smaller than that of thepatient's annulus in its natural, pre-diseased state.

Annuloplasty rings have also been developed in various shapes andconfigurations over the years in an effort to correct MR and otherconditions which reduce the functioning of the valve. For example,Carpentier, et al. in U.S. Pat. No. 4,055,861 disclosed two semi-rigidsupports for heart valves, one of which being closed (or D-shaped) andthe other being open (or C-shaped). In the closed configuration, thering is generally flat about an anterior-posterior plane, and has aconvex posterior side and a generally straight anterior side. U.S. Pat.Nos. 5,104,407, 5,201,880, and 5,607,471 disclose closed annuloplastyrings that are bowed slightly upward on their anterior side. Because theanterior aspect 26 of the mitral annulus is fibrous and thus relativelyinflexible (at least in comparison to the posterior aspect 28), theupward curve in the anterior side of each ring conforms the ring moreclosely to the anatomical contour of the mitral annulus, and thusreduces undue deformation of the annulus.

It should be noted here that correction of the aortic annulus requires aconsiderably different ring then with a mitral annulus. For example,U.S. Pat. Nos. 5,258,021 and 6,231,602 disclose sinusoidal or so-called“scalloped” annuloplasty rings that follow the up-and-down shape of thethree cusp aortic annulus. Such rings would not be suitable forcorrecting a bicuspid valve deficiency.

While good results in the treatment of CHF and MR have been obtained inthe preliminary applications of the above-described methods andapparatuses, it is believed that these results can be significantlyimproved. Specifically, it would be desirable to produce a mitralannuloplasty ring that can re-shape the mitral annulus in a way thatwill significantly repair the geometric configuration of the leftventricle wall beyond that which has been observed with undersizedrings.

SUMMARY OF THE INVENTION

The present invention provides a number of annuloplasty rings forimplantation in a mitral valve annulus that correct both the annulus andhelp mitigate the effects of congestive heart failure. In one aspect,the invention provides an annuloplasty ring that has a generallyoval-shaped ring body defining an anterior portion, a posterior portionopposite the anterior portion, right and left sides between the anteriorand posterior portions, and transition segments between the sides andthe posterior portion. The ring body is oriented about a central axishaving an upward direction and a downward direction, the downwarddirection corresponding to the direction of blood flow through themitral valve annulus. The ring has, in plan view perpendicular to thecentral axis, a longer dimension along a major axis than a shorterdimension along a minor axis, and the posterior portion rises upwardfrom the adjacent transition segments to an axial position higher thanthe highest axial position of the anterior portion.

Desirably, the posterior portion extends radially inward from theadjacent transition segments to a radial position along the minor axisthat is closer to the central axis than an imaginary posteriorprojection in plan view of the sides toward each other. Preferably, theposterior portion extends radially inward from the adjacent transitionsegments to a radial position that is about 30-50% closer to the centralaxis than the imaginary posterior projection of the sides toward eachother.

In accordance with a one embodiment of the present invention, the ringis substantially saddle-shaped with the sides curving upward between theanterior portion and adjacent transition segments. The right and leftsides may rise to axial positions above the highest axial position ofthe anterior portion. The posterior portion rises upward from theadjacent transition segments to an axial position approximately equal toor above the highest axial positions of the right and left sides.Alternatively, the ring may be generally planar except for the posteriorportion which rises to an elevated axial position.

In another embodiment, the sides and transition segments are generallycurvilinear and the junctures between adjacent sides and transitionsegments are generally rounded. The posterior portion desirably alsoextends radially inward from the adjacent sides to a radial positionalong the minor axis that is closer (preferably about 30-50% closer) tothe central axis than an imaginary posterior projection in plan view ofthe sides toward each other.

The ring body is preferably comprised of a material having a highmodulus of elasticity that will substantially resist distortion whensubjected to the stress imparted thereon when the ring is implanted inthe mitral valve annulus of an operating human heart. For example, thering can be comprised of a ceramic material such as Steilite, titanium,Elgiloy, graphite, ceramic, hardened plastics, composite, or Nitinol®materials. The annuloplasty ring may further comprise an outer sewingsheath surrounding the ring body, the sewing sheath being formed of amaterial that will permit the passage of sutures therethrough forsecuring to ring to a mitral annulus.

The present invention also provides a mitral annuloplasty ringcomprising a ring body made of a material having a high modulus ofelasticity that will substantially resist distortion when subjected tothe stress imparted thereon when the ring is implanted in the mitralvalve annulus of an operating human heart. The ring body is orientedabout a central axis having an upward direction and a downward directioncorresponding to the direction of blood flow through the mitral valveannulus, and has a posterior bow that extends both radially inward andaxially upward. Desirably, the ring body has an anterior portion, aposterior portion opposite the anterior portion, right and left sidesbetween the anterior and posterior portions, and transition segmentsbetween the sides and the posterior portion. The ring body may besubstantially saddle-shaped with the sides curving upward between theanterior portion and adjacent transition segments. In a preferredembodiment, a mid-section of the posterior portion bows upward from theadjacent transition segments to an axial position higher than thehighest axial position of either of the right or left sides. Also, theright and left sides each may rise upward from the adjacent transitionsegments to an axial position above the highest axial position of theposterior portion.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a cross-sectional view along an anterior-posterior planethrough the left side of a heart illustrating healthy aortic and mitralvalves and annuluses;

FIG. 1B is a plan view of a healthy mitral valve and annulus;

FIG. 2A is a cross-sectional view along an anterior-posterior planethrough the left side of a heart illustrating a condition in the mitralvalve that leads to mitral regurgitation (MR);

FIG. 2B is a plan view of the mitral valve of FIG. 2A;

FIG. 3A is a cross-sectional view along an anterior-posterior planethrough the left side of a heart illustrating the implantation of aconventional annuloplasty ring to restore the mitral valve to itshealthy configuration;

FIG. 3B is a plan view of the restored mitral valve of FIG. 3A;

FIG. 4A is a cross-sectional view along an anterior-posterior planethrough the left side of a heart illustrating the implantation of anannuloplasty ring of the present invention to restore the mitral valveto an over compensated position that will foster LV remodeling;

FIG. 4B is a plan view of the restored mitral valve of FIG. 4A;

FIG. 5 is a perspective view of an inner support for an annuloplastyring of the present invention;

FIGS. 6A-6C are top plan, front elevational, and side elevational views,respectively, of the annuloplasty ring of FIG. 5;

FIGS. 7A-7B are front and side elevational views, respectively, of analternative annuloplasty ring of the present invention;

FIGS. 8A-8C are perspective, front elevational, and side elevationalviews of a further alternative annuloplasty ring of the presentinvention;

FIGS. 9A-9D are various views of a further exemplary annuloplasty ringof the present invention;

FIGS. 10A-10D are various views of a still further exemplaryannuloplasty ring of the present invention; and

FIGS. 11A-11C are various views of another exemplary annuloplasty ringof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Applicant has determined that congestive heart failure (CHF) andsecondary mitral regurgitation (MR) can be addressed with a newgeneration mitral annuloplasty ring. The ring when implanted not onlymodifies the circumference of the mitral annulus as do existingannuloplasty rings, but it also elevates and/or reconfigures theposterior portion of the mitral annulus so as to mold and re-shape thegeometry of the left ventricle.

The attached figures illustrate several exemplary embodiments of theannuloplasty ring of the present invention, which can be described asbeing continuous and having an anterior side, a posterior side and rightand left sides. All of the sides are generally curvilinear with nospecific demarcations to indicate abrupt transitions therebetween.Rather, smooth transitional sections between the adjacent sides providecurvilinear connections that give the ring a generally rounded (i.e.,oval) configuration.

With reference to FIGS. 4A and 4B, a first exemplary mitral annuloplastyring 50 of the present invention is shown implanted in the mitralannulus 20. As seen in FIG. 4A, the posterior aspect 28 of the mitralannulus rises axially upward by a distance z from the datum plane 32 ofthe annulus when healthy. In addition, as seen in FIG. 4B, theanterior-posterior dimension 38 of the mitral annulus has been reducedby the annuloplasty ring 50. These two corrections to the mitral annulusare accomplished by a specially shaped posterior portion 52 of theannuloplasty ring 50, and because the ring is made relatively rigid.Because of the elevation of the posterior aspect 28 of the mitralannulus, the left ventricular wall 36 is molded and re-shaped, whichhelps mitigate some of the effects of CHF.

The degree to which a mid-section of the posterior portion 52 risesdepends on multiple variables including specific patient pathology andthe overall ring size, but it is projected that for applications in mostadult sized hearts the preferable rise will be about 3-5 millimeters.Unlike prior annuloplasty rings, this configuration is not intended tofollow the natural curvature of the mitral annulus. Rather, when theannuloplasty ring 50 is implanted in a mitral annulus, the“over-correcting” upward curvature of the ring 50 imparts a unique shapeto the annulus that has the effect of molding and reshaping both themitral annulus and the left ventricle. It is believed that this moldingand reshaping of the geometry of the left ventricle will reduce theseverity of CHF which in turn will reduce strain on the mitral valve andcorresponding MR (and vice versa). In other words, this ring provides anannular solution to address ventricular pathology.

The exemplary annuloplasty ring 50 of FIGS. 4A and 4B is shown in moredetail in FIGS. 5-6C. For purpose of orientation, FIG. 5 illustratesorthogonal axes wherein the Z-axis lies along of the axis of blood flowthrough the ring when implanted, and the X- and Y-axes generally definethe datum plane 32 as mentioned above. It will further be understoodthat the positive Z direction illustrated in FIG. 5 is the “upward”direction, the negative Z direction is the “downward” direction, and thering is designed to be implanted in a mitral annulus such that bloodwill flow in the downward direction.

As seen in FIG. 6A, the X-axis extends across the ring in theanterior-posterior direction illustrating a minor axis dimension 54. TheX-axis typically lies in a plane of symmetry of the ring 50 such thatthe left side and right side are identical. The Y-axis extends acrossthe long dimension of the ring 50 such that a major axis dimension 56 isdefined. As with many conventional rings, the ratio of the minor axisdimension 54 to the major axis dimension 56 is about 3:4. Although notgeometrically precise, such a ring configuration may be considered ovalor elliptical.

As seen in FIG. 6A, the annuloplasty ring 50 includes the speciallyshaped posterior portion 52, an anterior portion 60, and a pair ofgenerally symmetric side portions 62 a, 62 b. As can be seen from theperspective of FIG. 5, two relatively sharply curved transition segments64 a, 64 b join either side of the posterior portion 52 to the sideportions 62 a, 62 b.

With reference also to FIGS. 6B and 6C, the relative elevations in theZ-axis of the various portions of the ring 50 are shown in FIG. 5. FIG.6B shows that the transition segments 64 a, 64 b are located at thelowest points about the ring 50 when in its “horizontal” orientationover an X-Y reference plane 70. A mid-section of the shaped posteriorportion 52 arcs upward between the transition segments 64 a, 64 b andhas its highest point on the X-Z plane. Likewise, the two side portions62 a, 62 b arc gently upward from the respective transition segments 64a, 64 b and then gradually curve downward into a blended transition withthe anterior portion 60. As seen in the background of FIG. 6B, theanterior portion 60 exhibits a slight upward bow centered along the X-Zplane, and preferably rises to the same height as the shaped posteriorportion 52. The overall contour of ring 50 around its periphery isundulating or serpentine. If a three-dimensional surface were drawnacross the open middle of the ring to conform as much as possible to theperiphery of the ring 50, that surface would be somewhat saddle-shapedwith upward bows along the Y-Z and X-Z planes. (To further illustratethe overall shape of the ring 507 it somewhat resembles a molded potatochip sold under the Pringles brand.) The extent of upward curvature forthe ride and left side portions 62 a, 62 b may reach as high, or higher,than that of the posterior portion 52, but do not necessarily need toextend this high. This too will depend on multiple factors includingpatient pathology.

The difference in elevation between the shaped posterior portion 52 andthe adjacent transition segments 64 a, 64 b is shown at z_(A) in FIG.6B. The subscript “A” refers to the point A around the ring 50 peripheryas indicated in FIG. 6A. The midpoint of the anterior portion 60 isdenoted at B, while the points along the side portions 62 a, 62 b thatlie on the Y-Z plane are denoted at C. The lowest points in thetransition segments 64 a, 64 b are denoted at D, while lowest pointsalong the anterior portion 60 are denoted at E. The elevational at eachof these points is represented as z_(A), z_(B), z_(C), z_(D), and z_(E).It should be noted also that the elevations are as measured to thebottom of the ring 50, although the thickness of the ring means that theoverall height is somewhat greater. When viewed with reference to theplane 70, z_(D) is at zero. In this embodiment, z_(A)=z_(B)=z_(C), but,as will be described below, z_(A) may be substantially greater thaneither z_(B) or z_(c), and z_(B) is desirably larger than z_(C).

FIGS. 5-6C also illustrate a second aspect of the present invention,namely that a mid-section of the posterior portion 52 extends inward toa radial position that is closer to the central axis than if the rightand left side portions 62 a, 62 b projected smoothly toward one another.This too results in a reshaping effect on the mitral annulus, which inturn reshapes the left ventricle geometry.

With reference again to FIG. 6A, a phantom projection or extension 72 ofthe two side portions 62 a, 62 b is indicated. This arcuate imaginaryextension 72 has been drawn to illustrate the inward bow of the shapedposterior portion 52. That is, the posterior portion 52 diverges inwardfrom this imaginary ring projection, which represents conventionaloval-shaped rings of the prior art. Specifically, the posterior portion52 bows inward at point A, a distance indicated as x_(A). As with theaxial correction noted above, the degree to which the posterior portion52 extends inward will depend on multiple variables, but it ispreferable that the innermost position of the posterior side be about30-50% closer to the central axis than the arcuate imaginary extension72. Of course, the distance x_(A) varies depending on the overall sizeof the ring 50.

With reference again to FIGS. 4A and 4B, the effect of the inward andupward posterior portion 52 of the ring 50 as implanted can be seen. InFIG. 4A, the posterior portion 52 causes the posterior portion 28 of themitral annulus 20 to elevate above the datum plane 32 the distance z.This shift in the mitral annulus 28 places the left ventricular wall 36in greater tension than normal and helps re-shape and recondition thatwall to help rectify the detrimental effects of CHF. Furthermore, notonly does the ring 50 elevate the posterior portion 28 of the mitralannulus 20, but it also pulls that side of the annulus radially inward,as indicated in FIG. 4B. The anterior-posterior dimension 38″ is shownreduced from its normal dimension (the normal dimension is essentiallyrepresented in FIG. 3B as 38′).

FIGS. 7A and 7B show front and side elevational views of an alternativeannuloplasty ring 100 of the present invention that shares some offeatures of the annuloplasty ring 50 described above. For example, theoverall contour of ring 100 bows upward along the Y-Z plane as indicatedin FIG. 7B, and a mid-section of a posterior portion 102 is bothupwardly (see FIG. 7A) and inwardly (see FIG. 7B) displaced from animaginary continuation of the side portions of the ring. As seen bestfrom the front in FIG. 7A, the ring 100 does not have a serpentineconfiguration as with the earlier-described ring 50, instead the profilefrom the front lies generally in a single arc with the posterior portion102 elevated relatively suddenly therefrom.

FIG. 7B shows that the middle segment 104 of the anterior side of thering also bows inwardly from the adjacent sides to a radial positionalong the X-axis that is closer to the central axis than an imaginaryanterior projection in plan view of the adjacent sides toward eachother. The inward curve of the anterior segment 104 further reduces thedimension of the repaired annulus in the anterior-posterior plane, andcontributes to pulling the posterior aspect of the annulus inward and atthe same time conditioning the left ventricular wall.

FIGS. 8A-8C illustrate a generally planar annuloplasty ring 110 of thepresent invention having an anterior portion 112, an opposing posteriorportion 114, and left and right sides 116 a, 116 b. A mid-section of aposterior portion 114 is substantially the same as the posterior portion102 in FIGS. 7A and 7B such that it bows inward and upward. As in theearlier version, the anterior portion 112 bows inwardly, although theentire periphery of the ring 110 except for the posterior portion 114lies in a plane.

FIGS. 9A-9D illustrate an alternative annuloplasty ring 130 of thepresent invention that, as viewed in plan view in FIG. 9B, is symmetricboth about the X-Z plane and the Y-Z plane. The ring 130 is notsymmetric in elevation, as seen in FIGS. 9C and 9D, wherein amid-section of a posterior portion 132 rises upward and curves inward.As with the embodiment of FIGS. 8A-8C, the entire ring 130 lies in aplane except for the posterior portion 132. Again, the particularconfiguration of the posterior portion 132 helps re-shape the mitralannulus and recondition the left ventricular wall. Moreover, an anteriorportion 132 also bows inward to help reduce the size of the mitralannulus in the anterior-posterior direction. As explained above, theterm “bows inward” refers to the diversion of the particular portionfrom an imaginary curve that would continue the oval peripheral planview of the ring.

FIGS. 10A-10D show another ring 150 of the present invention that isnearly identical to the ring shown in FIGS. 9A-9D, except for aposterior portion 152. As seen best in FIGS. 10C and 10D, a mid-sectionof the posterior portion 152 rises at sharp transitions 154 from therest of the ring 150 which is planar. Rather than a gentle upward andinward curvature, a short upward segment 156 connects a middle, inwardlycurved segment 158 to each of the transitions 154. This embodiment ofthe ring 150 thus illustrates that specially shaped portions around theperiphery do not necessarily have to join with the remainder of the ringin gentle blended curves.

FIGS. 11A-11C are plan, front elevational, and side elevational views,respectively, of a still further annuloplasty ring 170 that is generallyoval-shaped about a major axis 172 and a minor axis 174. The points A,B, C, D and E are located in the same places as described above withrespect to FIG. 6A-6C. A mid-section 176 of a posterior portion of thering 170 bows upward and inward. The elevation z_(A) above a datum plane178 is seen in FIG. 11B, while the magnitude of inward bow x_(A) is seenin FIG. 11A. The sides 180 a, 180 b also bow upward a distance z_(C) asindicated in FIG. 11B. Finally, an anterior portion 182 bows upward adistance z_(B) and inward a distance x_(B). In this embodiment,z_(A)≠z_(B)≠z_(C). The mid-section 176 forms a plateau 184 in theZ-direction centered about the minor axis 174 and having a dimension yas seen in FIG. 11B. The dimension y is desirably about 2 mm. Thisplateau 184 helps prevent kinking of a tubular fabric or othersuture-permeable covering over the posterior portion because of thegreater upward and inward bow in comparison to other rings describedherein.

Exemplary dimensions for a 28 mm ring 170 include the followingrelations:

-   -   0<z_(B)<z_(A), and preferably,    -   0.10 z_(A)≦z_(B)≦0.20 z_(A), and more preferably,    -   z_(B) about 0.14 z_(A).

Furthermore:

-   -   z_(C)>z_(B), and,    -   0<z_(C)≦z_(A), and preferably,    -   0.20 z_(A)≦z_(C)≦0.40 z_(A), and more preferably,    -   z_(c)=about 0.28 z_(A).

Finally,

-   -   3 mm<z_(A)≦8 mm, and preferably,    -   z_(A)=about 7 mm.

These relations and exemplary dimensions may be suitable for all sizesof rings, or may be scaled up or down proportionally.

The inward bow x_(A) is desirably about 40% of the distance along theminor axis from point B to point I regardless of the ring size. Point Iis the location of the mid-point of an imaginary posterior projection inplan view of the sides 180 a, 180 b toward each other. The anteriorinward bow x_(B) is desirably about 1 mm.

The ideal degree to which the posterior and/or anterior sides are moldedinward and upward according this invention depend on multiple factors.Preferably however, these features will be exaggerated to an extent thatthe mitral annulus is “over-corrected.” In other words, an importantfactor of this invention is that the mitral annulus not be just repairedto its natural, pre-diseased state, but that the annulus actually bereduced past that point to an extent that will significantly affect thegeometry of the left ventricle. Initial studies suggest that the inwardand/or upward corrections for the posterior side be about 30-50% beyondthat which would bring the annulus to its pre-diseased state.

The annuloplasty rings herein are desirably made of a single innermember as illustrated, covered with a suture-permeable outer layer. Asopposed to flexible annuloplasty rings that are designed simply toreduce the circumference of the mitral annulus, the annuloplasty ring ofthe present invention must be quite stiff. It must substantially retainits shape in opposition to the stresses that will be imparted by musclesof the heart through out each beating cycle. Accordingly, this ring mustbe made from a material having a relatively high modulus of elasticity.For example, the inner member as shown may be machined or molded ofStellite, polished, and then covered with a polyterapthalate fabric.Alternatively, an intermediate silicone sleeve around the inner membermay be used. Stellite provides a desired rigidity to best facilitatereshaping of the annulus and left ventricle, although more commonly usedmaterials such as titanium, Elgiloy, graphite, ceramic, hardenedplastics, or Nitinol® may be substituted.

The ring also preferably includes an outer sewing sheath that permits itto be sutured into the mitral annulus. The sewing sheath should besufficiently porous and/or flexible to permit sutures to be passedtherethrough, but it must not be so flexible as to counteract thestiffness requirements discussed above. Because the ring will be undersuch loads, it will also be necessary to insert more sutures in thesewing sheath than for more flexible rings (to reduce the loads onindividual sutures). For example, if traditional rings require in theneighborhood of 8 to 10 stitches around the circumference, the presentannuloplasty ring might require as many as 20-30 or more.

It will be understood by those of skill in the art that the embodimentsdescribed above can be incorporated individually or in combination.While each aspect will have the desired effect of and reshaping themitral annulus and left ventricle, it is the re-shaping of the posteriorside that will have the greatest effect of molding and re-shaping theleft ventricle. The aspect of extending the anterior side radiallyinward will preferably not be used unless the posterior side has alsobeen configured as described herein.

It will also be readily apparent that reshaping the mitral valve annuluswith the present annuloplasty ring will cause the mitral leaflets tocoapt in a new location. However, those of skill in the art willrecognize that this slight realignment of the leaflets is acceptable,and often even preferable.

It will be appreciated by those of skill in the relevant art thatvarious modifications or changes may be made to the examples andembodiments of the invention described in this provisional application,without departing from the intended spirit and scope of the invention.In this regard, the particular embodiments of the invention describedherein are to be understood as examples of the broader inventive conceptdisclosed in this application.

1. A mitral annuloplasty ring for implantation in a mitral valve annulushaving an anterior aspect and a posterior aspect, the annuloplasty ringcomprising: a continuous ring body having an anterior portion, aposterior portion opposite the anterior portion, right and left sidesbetween the anterior and posterior portions with transition segmentsbetween the sides and the anterior and posterior portions; wherein thering body is oriented about a central axis having an upward directionand a downward direction, the downward direction corresponding to thedirection of blood flow through the mitral valve annulus, the ringhaving in plan view perpendicular to the central axis a major axis and aminor axis; wherein the anterior portion has an upward bow, and, whereinthe posterior portion has an upward bow.
 2. The annuloplasty ring ofclaim 1, wherein the ring is substantially saddle-shaped with the rightand left sides also having upward bows.
 3. The annuloplasty ring ofclaim 2, wherein the right and left sides each rise upward to an axialposition about the same level as the anterior portion.
 4. Theannuloplasty ring of claim 1, wherein both the anterior and posteriorportions have approximately equal height upward bows.
 5. Theannuloplasty ring of claim 1, wherein the posterior portion bowsradially inward to a radial position along the minor axis that is closerto the central axis than an imaginary posterior projection in plan viewof the sides toward each other.
 6. The annuloplasty ring of claim 5,wherein the radial position is about 30-50% closer to the central axisthan the imaginary posterior projection in plan view of the sides towardeach other.
 7. The annuloplasty ring of claim 5, wherein the anteriorportion of the ring bows radially inward to a radial position along theminor axis that is closer to the central axis than an imaginary anteriorprojection in plan view of the sides toward each other.
 8. Theannuloplasty ring of claim 1, wherein the ring body is comprised of amaterial having a high modulus of elasticity that will substantiallyresist distortion when subjected to the stress imparted thereon when thering is implanted in the mitral valve annulus of an operating humanheart.
 9. The annuloplasty ring of claim 8, wherein the ring iscomprised of titanium.
 10. The annuloplasty ring of claim 1, wherein thering body periphery comprises gentle blended curves except in theposterior portion which exhibits a relatively sudden elevation fromadjacent sides.
 11. A mitral annuloplasty ring for implantation in amitral valve annulus having an anterior aspect and a posterior aspect,comprising: a continuous ring body made of a material having a highmodulus of elasticity that will substantially resist distortion whensubjected to the stress imparted thereon when the ring is implanted inthe mitral valve annulus of an operating human heart, the ring bodybeing oriented about a central axis having an upward direction and adownward direction, the downward direction corresponding to thedirection of blood flow through the mitral valve annulus, the ringhaving in plan view perpendicular to the central Z axis a major Y axisand a minor X axis, the ring body having an anterior portion, aposterior portion opposite the anterior portion, and right and leftsides between the anterior and posterior portions, and wherein the ringhas equal height upward axial bows on both the anterior and posteriorportions.
 12. The annuloplasty ring of claim 11, wherein the ring bodyis substantially saddle-shaped with the right and left sides also havingupward bows.
 13. The annuloplasty ring of claim 12, wherein the rightand left side upward bows are about the same height as a height of theanterior portion.
 14. The annul oplasty ring of claim 11, wherein boththe anterior and posterior portions bow upward to axial positions abovethe height of the right and left sides.
 15. The annuloplasty ring ofclaim 11, wherein the posterior portion bows radially inward to a radialposition along the minor axis that is closer to the central axis than animaginary posterior projection in plan view of the sides toward eachother.
 16. The annuloplasty ring of claim 15, wherein the radialposition is about 30-50% closer to the central axis than the imaginaryposterior projection in plan view of the sides toward each other. 17.The annuloplasty ring of claim 1, wherein the anterior portion of thering bows radially inward to a radial position along the minor axis thatis closer to the central axis than an imaginary anterior projection inplan view of the sides toward each other.
 18. A mitral annuloplasty ringfor implantation in a mitral valve annulus having an anterior aspect anda posterior aspect, said annuloplasty ring comprising: a continuous ringbody having an anterior portion, a posterior portion opposite theanterior portion, right and left sides between the anterior andposterior portions with transition segments between the sides and theanterior and posterior portions, wherein the ring body is oriented abouta central axis having an upward direction and a downward direction, thedownward direction corresponding to the direction of blood flow throughthe mitral valve annulus, the ring having in plan view perpendicular tothe central axis a major axis and a minor axis, wherein the ring body issubstantially saddle-shaped with the anterior and posterior portionshaving upward bows, and the right and left sides also having upwardbows, and wherein the anterior and posterior portions bow radiallyinward to radial positions along the minor axis that are closer to thecentral axis than imaginary anterior and posterior projections in planview of the sides toward each other.
 19. The annuloplasty ring of claim18, wherein the posterior portion bows radially inward to a radialposition along the minor axis that is about 30-50% closer to the centralaxis than the imaginary posterior projection in plan view of the sidestoward each other.
 20. The annuloplasty ring of claim 18, wherein theposterior portion bows radially inward farther than does the anteriorportion.
 21. The annuloplasty ring of claim 18, wherein the posteriorportion upward bow is higher than the anterior portion upward bow. 22.The annuloplasty ring of claim 21, wherein the anterior portion upwardbow is 10-20% of the height of the posterior portion upward bow.
 23. Theannuloplasty ring of claim 18, wherein the posterior portion upward bowrises about 3-8 mm above adjacent transition segments.
 24. Theannuloplasty ring of claim 18, wherein the posterior portion isgenerally rounded except for a plateau at its highest point on the minoraxis.
 25. The annuloplasty ring of claim 18, wherein the ring body iscomprised of a material having a high modulus of elasticity that willsubstantially resist distortion when subjected to the stress impartedthereon when the ring is implanted in the mitral valve annulus of anoperating human heart.